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Aim. To analyze various strategies aimed at mitigating complications of the portal hypertension syndrome at the Minsk Scientific and Practical Center for Surgery, Transplantology, and Hematology.Material and methods. Patients who had undergone different types of treatment were retrospectively observed: shunt surgery to form portacaval anastomoses, transjugular portosystemic shunt placement, and liver transplantation. The following parameters were analyzed: incidence of complications, hospital mortality rate, survival rate, and perioperative indicators.Results. Since 1980, 131 shunt surgeries have been performed at the Center, while 880 liver transplantations and 232 transjugular portosystemic shunt placement procedures have been performed since 2008. Among 68 patients with compensated cirrhosis who had undergone shunt placement, no hospital mortality rate was reported, whereas in patients with Child-Pugh B cirrhosis and Child–Pugh C cirrhosis, it reached 19.5% and 87.5%, respectively. Following TIPS, the overall case mortality rate amounted to 9.9% (following TIPS prior to transplantation – 8.2%, following TIPS used as the final treatment – 12.8%). After liver transplantation, in-hospital mortality rate reached 7.7%.Conclusion. Over 50 years, the strategy for managing portal hypertension has undergone significant changes due to the establishment of institutions providing a complete cycle of all treatment measures for such patients. Patients suffering from the complications of the portal hypertension syndrome tend to receive the most effective treatment in hospitals having experience in rational conservative therapy, endovascular procedures, and transplantation.

A novel two-cylinder single-stage piston hybrid power machine with liquid movement effectuated by vacuum on the suction side is described. The presented results of an experimental study on the cooling efficiency of the cylinder-piston group and the effect of compressor cooling on the feed rate show that the temperature of the valve plate decreases by 10–12 K, while that of the cylinder walls decreases by 7–8 K. Based on the analysis of the working processes of a reciprocating compressor, the effect of cooling on the feed rate was found to be ambiguous, leading both to its possible increase and reduction; this was confirmed as a result of experimental studies.

Recent judicial practice regarding the interpretation of the ‘controlled group’ in order to apply exceptions from prohibition on cartel agreements is controversial. Taking advantage of the uncertainty that has arisen, many participants in cartel cases make attempts (and sometimes successfully) to prove that in fact the conspiracy took place within a controlled group, and, therefore, was permissible. In this article we will consider the most common arguments used by business entities in cases of cartels and evaluate the possibility of their application in modern conditions.

The present article considers operating processes occurring in a positive displacement two-stage piston hybrid energy-generating machine having a gas cap. The conducted numerical experiment revealed the physical picture of viscous fluid flow, as well as the features associated with implementing a mathematical model of these operating processes. It was found that a change in any of the independent parameters leads to a corresponding change in the amount of fluid entering the second-stage working chamber of the machine, the maximum and minimum fluid levels, the liquid piston stroke, clearance space volume, as well as the amount of fluid ejected into the compressor discharge line. The presented ranking of the obtained results shows that the discharge pressure of compressible gas has the greatest influence on the operating processes.

The paper proposes a method for calculating the kinematic parameters (acceleration, speed, and displacement) and inertial losses of a liquid piston head in the profiled working chamber of the second stage of a piston hybrid energy-generating machine (PHEM). The working chamber is formed by two rotating truncated cones. Using a continuity equation of fluid flow in the machine, a general expression is obtained for determining the acceleration of the surface layer of the liquid piston when changing the geometry of the working chamber. The solution is reduced to an analytical form. The numerical experiment made it possible to evaluate the effect of changing the geometry of the working chamber on the kinematic parameters of the liquid piston and inertial head losses in the working chamber of the second stage of the PHEM.

This paper examines the use of various types of cooling liquids in a two-cylinder single-stage piston hybrid power machine with fluid flow due to vacuum at suction. Liquids with various basic thermal properties were used as working fluids: distilled water, antifreeze, and transmission oil. Specific heat capacities and dynamic viscosities of these liquids differed from 2 to 10 times. The experimental studies showed that the greatest cooling effect on the cylinder-piston group was observed when using distilled water, and the least — when using transmission oil. The average surface temperature of the working chamber when cooled with water was minimal in the range of 330–340 K. The average surface temperature of the working chamber when cooled with transmission oil was maximum and ranged from 345 to 355 K, i. e. it was about 15 K higher than when cooled with water. The average surface temperature of the working chamber when cooled with antifreeze occupied an intermediate position between the average temperatures of the working chamber when cooled with water and that with transmission oil and was in the range of 335–345 K, i. e. about 5 K higher than when cooled with water.

This article presents a method for calculating the dynamics of fluid motion in a two-stage hybrid energy machine with a gas cap. The developed method is based on the Bernoulli energy conservation equation, taking the linear hydraulic resistances, local hydraulic resistances, and inertial forces into account. The expressions for the current coordinate values of the liquid levels and pressures in the gas cap apply to the second stage compressor section and the first stage pump section. The developed method of calculation can be used for the analysis of working processes in compressor machines based on the principle of the liquid piston.

Techniques of determining the velocities of a piston for performing isothermal and polytropic processes of compression in the absence of leakage in the second stage of the compressor section of a hybrid power machine are considered. The laws of variation of the velocities of the piston over time (relative to the crank angle) and their average value are determined. A comparison of the instantaneous and average velocities of the piston for performing isothermal and polytropic processes of compression to the instantaneous and average velocities of a piston possessing a crank drive is performed. It is shown that the isothermal process of compression is not practically realizable with the use of a crank drive, while the polytropic process of compression may be realized with index of polytropy 1.15–1.2 and higher.

Different methods of profiling the working cavity of the second stage of a volumetric hybrid piston power machine are considered. Profiling of the working chamber in order to achieve a constant velocity of the liquid piston and attain the maximal magnitude of the heat-exchange surface, as well as profiling of the surface of a working chamber consisting of a cone and cylinder are performed. Computational formulas in analytic form are obtained in order to create a profiled surface that satisfies the first two conditions. For the third condition criteria for estimating the efficiency relative to the maximal magnitude of the heat-exchange surface and relative to the deviation of the velocity of the liquid piston from some constant velocity of the liquid in the working chamber are developed. As a result of a numerical experiment forms of the working chamber that satisfy the first two conditions are established and it is proved that a conical surface is best for a working chamber consisting of a cone and cylinder.

The paper presents the world’s first clinical case of two full-term successive pregnancies in a patient following simultaneous liver-kidney transplantation with reno-portal transposition. Both pregnancies ended with the birth of healthy children and favorable course of postpartum and long-term periods. The features of management and childbirth are highlighted. Literature review on this problem is presented.

A prototype of a crossheadless hybrid piston power machine is developed based on a basic diagram protected by a patent for an invention. An experimental investigation of the crossheadless machine as well as of a crosshead hybrid piston power machines with a smooth, respectively, multistep groove seal is carried out. It is experimentally demonstrated that the surface temperature of the valve plate and the temperature of the intake gas developed by the new crossheadless hybrid piston power machine is, correspondingly, 10–15 K and 6–8 K lower than the comparable temperatures of a crosshead hybrid piston power machine with smooth, respectively, multistep slot seal. Improved cooling of the compressible gas makes it possible to increase the volume efficiency of the compressor section and its indicated efficiency.

An analysis of the processes involved in heating of the liquid present above a piston in the working cavity of the compressor section of a positive-displacement hybrid power machine is given. On the basis of the general fundamental laws of conservation of energy and mass a thermodynamic calculation of the parameters of a two-phase, two-component open thermodynamic system with deformation and thermal interaction of phases is carried out. The influence of deformation work, external heat exchange, and direct-contact heat transfer on the variation of the temperature of the liquid is determined.

Piston hybrid power machines combining the functions of a compressor and a pump in one unit have become widespread, with a new class of machines that do not have a crosshead currently under development. A prototype of such a machine was designed and manufactured based on the new concept of a crossheadless piston hybrid power machine. A plan for conducting a series of experimental studies was developed. The experimental studies confirmed the feasibility of the prototype in the entire range of independent operating parameters (discharge pressure in the compressor section, discharge pressure in the pump section, the number of revolutions of the crankshaft). The effect of operating parameters on the instantaneous and integral characteristics of the compressor and the pump sections of the crossheadless piston hybrid power machine was also assessed through the experimental studies.

A generalized approach to the analysis of feed unevenness in positive displacement pumps is considered. A procedure for calculating the working processes in chambers of constant or variable volume in a discharge line as well as a nonstationary one-dimensional gas flow in a discharge pipe is developed. Boundary conditions are defined. Nonstationary one-dimensional flow is calculated by the method of “characteristics.” By means of a numerical experiment, variations in the pressure in the working chambers and along the length of the pipe as a function of the turning angle of the shaft are established. On the basis of pressure fluctuation in a discharge pipe, it is proved that the feed unevenness significantly exceeds the magnitude of the feed unevenness determined when the pressure fluctuation is not taken into account.

Currently, one of the main ways to improve the efficiency of piston compressors and volumetric pumps is to combine them into a single unit, called a piston hybrid energy machine. Recently, a new class of crossheadless piston hybrid energy positive displacement machines has appeared. In this work, a comparison of mass-dimensional indicators of experimental crosshead and crossheadless hybrid energy machines is performed. The analysis of the results shows that the crossheadless machine has significantly smaller masses of moving parts performing reciprocating motion (almost 3 times) and a smaller maximal overall size (almost 1.5 times) in comparison to the crosshead machine. The specific mass-dimensional indicators of the two machines are comparable.

A mathematical model of the working processes in positive-displacement machines designed to compress two-phase, two-component working fluids is developed on the basis of the general laws of conservation of energy, mass, volume and motion. A mathematical model of the working processes of a hybrid piston power machine where there is a layer of liquid above the piston in the compressor section is given. Two open thermodynamic systems (gas and droplet liquid) in the presence of deformation and thermal interactions are considered.

The operation of a bulk-action hybrid piston power unit is described by a mathematical model based on the laws of energy, mass, and momentum conservation and the equation of state. The influence of the pressure in the pump and compressor sections, the gap in the compressor section, and the eccentricity on the relation between the opposing liquid flow rates through the piston seal and on the thickness of the liquid layer above the piston is analyzed.

The experimental dependencies of the quantity of liquid in the discharge line of the compressor section on the discharge pressures of the compressor and pump sections of a piston hybrid energy-generating machine having stepped slot seal are presented and analyzed. The dependencies of the characteristics of the studied machine on the slot seal gap sizes obtained in the numerical study are presented and analyzed.

Compression of the working fluid in bulk-action pumps (such as piston, gear-driven, and plate-type pumps) under the action of deformation, mass transfer, and heating is considered. A method of calculating the compression is developed, for each factor and for the combination of deformation and mass transfer. The effectiveness of compression is analyzed for each case.

The operation of a new stepped piston seal used in a hybrid piston power machine is described. The hydropneumatic design of the test bench is provided. A mathematical description of the working processes that occur in the seal is presented. Results of theoretical and experimental studies and an analysis of the influence of the angular spin rate of the crankshaft on the working processes and operational properties of a hybrid piston power machine are presented.

The results of experimental studies of piston hybrid energy-generating machine having smooth and stepped slot seals are analyzed. It is demonstrated that stepped piston seal is much more effective than the smooth one and raises the delivery factor of the compressor section by more than 10%, reduces the average temperature of the cylinder-piston group by 2–3 K, and enhances volumetric efficiency of the pump section by 3–5%.

The results of a numerical study and assessment of the influence of volumes of receivers and diameters of connecting fluid pipelines on the working processes and external characteristics of the studied machine are presented.

A procedure for calculating rational values of the nominal discharge pressures in the compressor and pump sections of a crossheadless hybrid power machine based on equality of volumes of mass flowing from the pump section to the compressor section and back in the course of the cycle is proposed. From a numerical experiment we are able to evaluate the influence of the main design and operating parameters on the ratio of the nominal discharge pressures in the compressor and pump sections. Based on the analysis, the principal methods of equalizing the nominal discharge pressures in the compressor and pump sections are determined.

A mathematical model of the working processes of a hybrid displacement piston power machine with profiled groove seal is proposed. Calculation of the working processes in the compressor section in the presence of a liquid film under the piston and a “pump” course in the pump section and a piston seal is presented. The working processes for a hybrid displacement piston power machine with a smooth groove seal and with a profiled groove seal is calculated and the influence of a profiled groove seal on the working processes and the dynamics of the layer of liquid over the piston is demonstrated.

The design of a piston hybrid power machine with a gas volume at the suction is given and the results of numerical study and analysis of the influence of crankshaft angular rotation speed on the characteristics of the studied machine are presented.

The principle of operation of a piston hybrid power machine with gas suction capacity is described. Results of a numerical investigation and analysis of the influence of the ratio of discharge pressure to suction pressure on the characteristics of the studied machine are given.

This article presents the results of long-term research on the basis of which unique technologies have been developed and implemented which one allowed to reduce the frequency of postoperative complications and to improve longterm results of treatment of patients with chronic liver diseases at the terminal stage, liver tumors, and fulminant hepatic failure.

The article is dedicated to the problem of pregnancy management and delivery after simultaneous liver-kidney transplantation (SLKT). The article contains general historic and statistic information, and presents the first real world clinical case of favorable pregnancy outcome in patient after simultaneous liver-kidney transplantation with reno-portal transposition.

Despite the fact that the key role of the liver in the formation of the immune response to injury is not in doubt, the mechanisms of weakening the immune response to infectious and noninfectious lesions in patients with hepatic failure remain unclear. We propose an original hypothesis of forming the ways to limit the amplitude of the systemic inflammatory response in patients with the end-stage liver disease. The basis of the hypothesis is the idea that as a result of reducing the intensity of the natural stimulation of membrane mCD14 receptors by the ligands of infectious nature, the basic mechanism of the systemic immune response induction by liver macrophages (Kupffer cells) is interrupted. According to the proposed hypothesis, in condition of liver failure, the synthesis of lipopolysaccharide-binding protein by hepatocytes is reduced. This leads to a decreased amplitude and intensity of the protective immune responses. This fact explains a number of clinical phenomena observed in patients with liver failure/dysfunction that consist in a reduced reactivity of the organism to the damage inflicted by infectious and noninfectious agents. The authors consider it possible to use this hypothesis in the search for new trends to prevent the immune system hyper-reactivity in sepsis, and to improve the therapeutic strategies for the management of patients at high risk of infectious complications after liver transplantation.

The effect of liquid compressibility in the two-stage piston hybrid positive-displacement machine with a liquid piston was considered. Based on the volume conservation equation, we developed a calculus methodology for the liquid compressibility during gas compression in the second stage of the compressor section. A numerical experiment made it possible to establish that some parameters have the greatest effect on the relative decrease in the height and velocity of the liquid layer. These parameters are the degree of pressure ratio; pipeline length; the polytropic index of the compression; the number of crankshaft revolutions. We found that the relative decrease in the liquid layer height is within 1 %, and the relative decrease in the liquid piston velocity is within 5 %. The paper analyses the liquid piston compressibility influence on the thermodynamic efficiency of the compression process and compressor performance.

Based on a study of processes developed upon desertification (salinization, solonetzization, and sand accumulation) in the soils of the Caspian Sea Lowland, it is shown that soil’s water retention capacity may be used as an integral parameter of all desertification trends. It is characterized by the water retention curve (WRC). The physical sense of the use of the WRC to characterize desertification consists in the fact that it shows the capability of soil to retain moisture and soil moisture mobility and availability for plants and thus characterizes the main edaphic factors, which limit biological productivity in natural ecosystems and the agroecosystems of arid regions. The soil WRC is a constant value without seasonal fluctuations, and this makes it universal in comparison with other soil parameters that undergo seasonal variations, thus making determination of the desertification rate difficult.

A technique of calculating the relationships between the discharge pressures in the pumping cavity and the compressor cavity of a hybrid energy-converting piston machine is proposed. Through the use of the results presented here, a relationship is found between the discharge pressure of the pumping cavity and that of the compressor cavity that assures equality between the mass flow rates of the liquid traveling out of the pumping and compressor cavities and, correspondingly, normal operation of a hybrid energy-converting piston machine.

The results of study of a piston hybrid machine that combines the function of a positive displacement pumpcum-compressor unit are reported. A distinctive feature of the studied machine is the presence between the piston and the cylinder wall of a slot seal made in the form of a hydrodiode. A numerical model of the motion of an incompressible viscous liquid in the channel of the hydrodiode made in 3D axisymmetric formulation is proposed. The turbulence effects are determined using SST (shear-stress transport) model. It is shown that the rate of liquid flow through the slot seal depends on the direction of motion. The physical nature of this phenomenon is analyzed.

In this work, a new liquid cooling system for a piston compressor based on pressure fluctuations of discharged gas is described. The developed method of calculation based on the fundamental laws of conservation of motion, mass, and energy recorded for gas and coolant is implemented in the form of a package of applied programs for the calculation of the cooling system of a single-stage piston compressor.